An implantable medical device (IMD) may wirelessly communicate with an external device. Wireless communication for IMDs may be at MICS radio frequencies (i.e., medical implant communications service radio frequencies between 402 MHz and 405 MHz), at ISM radio frequencies (i.e., industrial, scientific, and medical radio frequencies), or at other radio frequencies. The IMD may be a nerve stimulator (e.g., a vagus nerve stimulator), a pacemaker or other heart stimulation device, or another type of medical device. Wireless communication may enable the IMD to receive parameters, instructions, data, or combinations thereof, that specify operating characteristics of the IMD. Wireless communication may also enable the IMD to send information to the external device. The information may include operating parameters of the IMD, operation data, physiological data, power source information, and other data.
Wireless communication with an IMD can be problematic. For example, when the IMD has a conductive housing, and a communication antenna is located within the conductive housing, signals may be blocked or attenuated by the housing.